1. Field of the Invention
The present invention relates to a coolant passage structure of a small V-type liquid cooled engine mounted on a motor cycle, a small all terrain vehicle (hereinafter referred to as ATV), a snow mobile, a small leisure vehicle, a personal watercraft, or the like.
2. Description of the Related Art
Small liquid cooled engines (hereinafter also referred to as water cooled engines) are mounted on some of motor cycles, small all terrain vehicles (small ATV), snow mobiles, small leisure vehicles, personal watercrafts, and the like. In these water cooled engines, in general, low-temperature cooling water (coolant) cooled in a radiator is supplied from a water pump rotated by a drive shaft of the engine to water jacket(s) formed around a combustion chamber of the engine.
Conventionally, as described in Japanese Laid Open Patent Publication No. Hei 3-117614, in the small engine, for example, in the engine of the motor cycle, the water pump is placed in a lower portion of the engine and supplies coolant to water jacket(s) formed in engine cylinder(s) placed above the water pump via a hose or the like made of flexible rubber or the like.
In this case, however, the rubber hose around the engine of the motor cycle is visible from outside. These days, superior external appearance, not to mention high performance, is highly demanded of the motor cycle, the small all terrain vehicle, the leisure vehicle, and the like. Therefore, the placement of the rubber hose around the engine makes the entire engine portion complex in appearance regardless of how the external appearance of the engine itself is designed.
In addition, when using the rubber hose, the number of parts and man-hour for assembly of the engine are increased and a manufacturing cost of the engine portion is increased, in addition to the complex appearance described above.
Under the circumstances, an object of the present invention is to provide a coolant passage structure of a V-type liquid cooled engine, which makes an external appearance of the engine simple, and reduces the number of parts and man-hour for assembly for reduction of a manufacturing cost.
The present invention provides a coolant passage structure of a small V-type liquid cooled engine, wherein a water pump is provided in a cover provided on the engine or in the vicinity of the cover, comprising: a coolant passage provided in the cover for introducing the coolant from the water pump to the water jackets respectively formed in the cylinders of the engine.
With this coolant passage structure, the coolant passes through the coolant passage inside of the cover so that it is supplied from the water pump to the water jackets of the cylinders. Therefore, the conventional rubber hose becomes unnecessary and design of the external appearance of the engine portion can be made simple. In addition, this coolant passage structure makes a portion around the engine simple. Further, since the number of parts and man-hour for assembly of the engine can be reduced, this structure contributes to reduction of the manufacturing cost of the V-type liquid cooled engine.
It is preferable that the coolant passage structure of the small V-type liquid cooled engine, further comprises: a water gallery provided in a branch portion of the coolant passage for supplying the coolant to the respective cylinders arranged in V-shape, for introducing the coolant to the cylinders. With this coolant passage structure, the structure of the branch portion is simplified and the coolant can be supplied to the water jackets of the respective cylinders arranged in V-shape with loss of a pressure lessened.
It is preferable that in the coolant passage structure of the small V-type liquid cooled engine, the cover is a generator cover placed in a side portion of the engine.
It is preferable that in the coolant passage structure of the small V-type liquid cooled engine, the generator cover is attached to a crank case and the water gallery is formed in the crank case.
It is preferable that in the coolant passage structure of the small V-type liquid cooled engine, a rotational shaft of the water pump is identical to a rotational shaft of an oil pump to obtain a compact and reasonable configuration.